Gas turbine engine and method of operating thereof

ABSTRACT

A gas turbine engine and method for operating a gas turbine engine includes compressing an air stream in a compressor and generating a post combustion gas by combusting a compressed air stream exiting from the compressor in a combustor. The post combustion gas is expanded in a first turbine. The expanded combustion gas exiting from the first turbine is split into a first stream, a second stream and a third stream. The first stream of the expanded combustion gas is combusted in a reheat combustor. An outer liner and flame stabilizer of the reheat combustor are cooled using the second stream of the expanded combustion gas. An inner liner of the reheat combustor is cooled using the third stream of the expanded combustion gas and a portion of the second stream of the expanded combustion gas passing through the one or more flame stabilizers.

BACKGROUND

The disclosure relates generally to gas turbines engines, and inparticular, to cooling of a reheat combustor in a gas turbine engine.

A conventional gas turbine engine includes a compressor for compressingair (sometime referred to as an oxidant as the air has oxidizingpotential due to the presence of oxygen), which is mixed with fuel in acombustor and the mixture is combusted to generate a high pressure, hightemperature gas stream, referred to as a post combustion gas. The postcombustion gas is expanded in a turbine (high pressure turbine), whichconverts thermal energy from the post combustion gas to mechanicalenergy that rotates a turbine shaft.

Generally, during the process of combustion in the combustor, the oxygencontent in the air is not fully consumed. As a result, the hot postcombustion gas, exiting from the high pressure turbine, is associatedwith approximately 15% to approximately 18% by mass of oxygen andtherefore has the potential of oxidizing more fuel. Some gas turbineengines, therefore, deploy a reheat combustor, where the post combustiongas is re-combusted after mixing with additional fuel. The re-combustedpost combustion gas is expanded in another turbine section (low pressureturbine) to generate additional power. The deployment of the reheatcombustor and the low pressure turbine therefore utilises the oxidizingpotential of the post combustion gas, thereby increasing the efficiencyof the engine.

The reheat combustors, however, during operation, possess a high demandfor cooling air, which is generally provided by extracting a stream ofair from the compressor. The extraction of air reduces the engineefficiency, as the stream of extracted air is unavailable for expansionin the high pressure turbine. The extraction of compressor air forcooling the reheat combustor therefore reduces the benefits of deployingthe reheat combustor.

In addition, in a reheat combustor including an open centerline, hotcombustion gasses are able to access an upstream intermediate pressureturbine (IPT) rear frame (diffuser). In a reheat combustor of thisdesign, flame stabilization devices are typically cantilevered from theouter radius inward, which leads to cooling issues for the flamestabilization devices. Typically, cooling air will need to be injectedthrough the flame stabilization devices, exiting into the hot combustiongases. This open centered design creates an imaginary flow boundarythrough symmetry, such that hot gases will be recirculated in a toroidalcell on the centerline. This flow pattern will circulate hot gas back tothe IPT rear frame structure, causing an increased active cooling needfor that structure and present hot gas issues circulating around theentire surface of the flame stabiliser. The unsteady nature of therecirculation zone will additionally present issues for the combustor'soverall stability.

It is therefore desirable to have an alternate method to cool a reheatcombustor without adversely affecting the engine efficiency.

BRIEF DESCRIPTION

These and other shortcomings of the prior art are addressed by thepresent disclosure, which a method for operating a gas turbine engine.

One aspect of the present disclosure resides a gas turbine enginecomprising: a compressor for compressing air; a combustor for generatinga post combustion gas by combusting a compressed air exiting from thecompressor; a first turbine for expanding the post combustion gas; asplitting zone for splitting an expanded combustion gas exiting from thefirst turbine into a first stream, a second stream and a third stream; areheat combustor for combusting the first stream of the expandedcombustion gas; and a pressure loss device for developing a pressuredifferential between the second stream and the third stream. An outerliner and one or more flame stabilizers of the reheat combustor arecooled using the second stream of the expanded combustion gas and aninner liner of the reheat combustor is cooled using the third stream ofthe expanded combustion gas and a portion of the second stream of theexpanded combustion gas exiting the one or more flame stabilizers.

Another aspect of the present disclosure resides in a method foroperating a gas turbine engine comprising: compressing an air stream ina compressor; generating a post combustion gas by combusting acompressed air stream exiting from the compressor in a combustor;expanding the post combustion gas in a first turbine; splitting anexpanded combustion gas exiting from the first turbine into a firststream, a second stream and a third stream; combusting the first streamof the expanded combustion gas in a reheat combustor; cooling an outerliner and a flame stabilizer of the reheat combustor using the secondstream of the expanded combustion gas; and cooling an inner liner of thereheat combustor using the third stream of the expanded combustion gasand a portion of the second stream of the expanded combustion gaspassing through the one or more flame stabilizers.

Yet another aspect of the disclosure resides in a method a method foroperating a gas turbine engine comprising: splitting a flow of anexpanded combustion gas from a first turbine into a first stream, asecond stream and a third stream; combusting the first stream of theexpanded combustion gas in a reheat combustor; cooling an outer linerand one or more flame stabilizers of the reheat combustor using thesecond stream of the post combustion gas; and cooling an inner liner ofthe reheat combustor using the third stream of the post combustion gasand a portion of the second stream of post combustion gas passingthrough the one or more flame stabilizers.

Various refinements of the features noted above exist in relation to thevarious aspects of the present disclosure. Further features may also beincorporated in these various aspects as well. These refinements andadditional features may exist individually or in any combination. Forinstance, various features discussed below in relation to one or more ofthe illustrated embodiments may be incorporated into any of theabove-described aspects of the present disclosure alone or in anycombination. Again, the brief summary presented above is intended onlyto familiarize the reader with certain aspects and contexts of thepresent disclosure without limitation to the claimed subject matter.

BRIEF DESCRIPTION OF THE FIGURES

The above and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 schematically illustrates a gas turbine engine in accordance withone or more embodiments shown or described herein;

FIG. 2 schematically illustrates a gas turbine engine with anaerodynamic coupling between a first and second turbine in accordancewith one or more embodiments shown or described herein;

FIG. 3 schematically illustrates a reheat combustor of a gas turbine inaccordance with one or more embodiments shown or described herein;

FIG. 4 schematically illustrates a splitting zone and a reheat combustorof a gas turbine engine in accordance with one or more embodiments shownor described herein; and

FIG. 5 schematically illustrates method a method for operating a gasturbine engine in accordance with one or more embodiments shown ordescribed herein.

DETAILED DESCRIPTION

The disclosure will be described for the purposes of illustration onlyin connection with certain embodiments; however, it is to be understoodthat other objects and advantages of the present disclosure will be madeapparent by the following description of the drawings according to thedisclosure. While preferred embodiments are disclosed, they are notintended to be limiting. Rather, the general principles set forth hereinare considered to be merely illustrative of the scope of the presentdisclosure and it is to be further understood that numerous changes maybe made without straying from the scope of the present disclosure.

The terms “first,” “second,” and the like, herein do not denote anyorder, quantity, or importance, but rather are used to distinguish oneelement from another. The terms “a” and “an” herein do not denote alimitation of quantity, but rather denote the presence of at least oneof the referenced items. The modifier “about” used in connection with aquantity is inclusive of the stated value, and has the meaning dictatedby context, (e.g., includes the degree of error associated withmeasurement of the particular quantity). In addition, the terms “first”,“second”, or the like are intended for the purpose of orienting thereader as to specific components parts.

Moreover, in this specification, the suffix “(s)” is usually intended toinclude both the singular and the plural of the term that it modifies,thereby including one or more of that term (e.g., “the opening” mayinclude one or more openings, unless otherwise specified). Referencethroughout the specification to “one embodiment,” “another embodiment,”“an embodiment,” and so forth, means that a particular element (e.g.,feature, structure, and/or characteristic) described in connection withthe embodiment is included in at least one embodiment described herein,and may or may not be present in other embodiments. Similarly, referenceto “a particular configuration” means that a particular element (e.g.,feature, structure, and/or characteristic) described in connection withthe configuration is included in at least one configuration describedherein, and may or may not be present in other configurations. Inaddition, it is to be understood that the described inventive featuresmay be combined in any suitable manner in the various embodiments andconfigurations.

As discussed in detail below, embodiments of the present disclosureprovide an reheat combustor with cooling and method for cooling a reheatcombustor of a gas turbine engine. This disclosure may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather these embodiments areprovided so that this disclosure will be thorough and complete and willfully convey the scope of the disclosure to those skilled in the art.

FIG. 1 illustrates a gas turbine engine 10 in accordance with anembodiment of the disclosure. The FIG. 1 illustrates a compressor 12, acombustor 14, a first turbine 16, a splitting zone 18, reheat combustor20, and a second turbine 22. An air stream 24 comprising atmospheric airis fed into the compressor 12 for compression to the desired temperatureand pressure. After compression, the air stream 24 exits the compressor12 as a compressed air stream 26 and is mixed with a fuel stream 28 inthe combustor 14. The mixture is ignited (combusted) in the combustor 14resulting in a high temperature, high pressure stream of a postcombustion gas 30. The post combustion gas 30 is expanded in the firstturbine 16 to convert thermal energy associated with the post combustiongas 28 into mechanical energy and exits the first turbine 16 as anexpanded combustion gas 32. According to an embodiment, the firstturbine 16 is coupled to the compressor 12 via a shaft 34 and drives thecompressor 12. In a specific embodiment, the first turbine 16 is a highpressure turbine.

The expanded combustion gas 32 is associated with certain amount ofunutilized heated oxygen (about 15% to about 18% by mass). Therefore,instead of releasing the expanded combustion gas 32 in the atmosphere,the gas turbine engine 10 deploys the reheat combustor 20 and the secondturbine 22 to generate additional power. According to an embodiment,prior to entering the reheat combustor 20, the expanded combustion gas32 is routed through the splitting zone 18, where the expandedcombustion gas 32 is split into three streams (illustrated in subsequentfigures). A first stream of the expanded combustion gas 32 is combustedin the reheat combustor 20, whereas a second stream of the expandedcombustion gas 32 is utilized for cooling an outer liner (describedpresently) of the reheat combustor 20 and a flame stabilizer (describedpresently) within the reheat combustor 20. A third stream of theexpanded combustion gas 32 is utilized for cooling an inner liner(described presently) of the reheat combustor 20. In addition, a portionof the second stream of the expanded combustion gas 32, subsequent topassing through a flame stabilizer, is utilized for cooling the innerliner of the reheat combustor 20, and in an embodiment, a hottestportion of the inner liner in a flame zone. Details of the splittingzone 18 and the splitting of the expanded combustion gas 32 are furtherdiscussed in conjunction with subsequent figures. In an embodiment,after utilized for cooling, the second stream of the expanded combustiongas 32 and the third stream of the expanded combustion gas 32 may bemixed with the combusted first stream in the reheat combustor 20 and themixture is fed into the second turbine 22 as a flow 33. It should benoted herein that the second stream of the expanded combustion gas 32and the third stream of the expanded combustion gas 32, after being usedfor cooling of the reheat combustor 20, may partially or entirelyparticipate in the combustion process within the reheat combustor 20. Inan alternate embodiment, the combusted first stream 58 is fed into thesecond turbine 22 as a flow 33, and at least one of a portion of thesecond stream of the expanded combustion gas 32 and a portion of thethird stream of the expanded combustion gas are used to cool the turbine22, with or without the addition of a compressor air flow. The flow 33is expanded in the second turbine 22 to generate power. In anembodiment, the second turbine 22 is coupled to the first turbine 16 bya shaft 36.

The FIG. 1 also illustrates a stream of compressor air 38 and a streamof compressor air 40 drawn from various stages of the compressor 12 forcooling of the first turbine 16 and the second turbine 22, respectively.Alternatively, or in addition to, a portion of the second stream ofexpanded combustion gas 32 and/or a portion of the third stream ofexpanded combustion gas 32 may be used to cool the second turbine 22.Conventionally, during operation of a gas turbine engine, air is drawnfrom various stages of the compressor for cooling the various componentssuch as the combustor, the reheat combustor and the high pressure andlow-pressure turbines. The use of compressor air for cooling the variouscomponents results in a loss of efficiency of the conventional gasturbine engine as the compressor air fraction is utilized for cooling isunavailable for complete acceleration and expansion in the high-pressureturbine. It should be noted herein that such loss of efficiency in theconventional gas turbine engine is greatest for the compressor air usedto cool the reheat combustor and the low-pressure turbine. The presentdisclosure proposes use of the expanded combustion gas 32 for coolingthe reheat combustor 20, thereby decreasing the quantity of compressorair extracted for cooling purposes and improving the efficiency.

In an embodiment of the disclosure, one of the second stream of theexpanded combustion gas 32 or the third stream of the expandedcombustion gas 32 is mixed with a coolant 42 and the mixture is utilizedfor cooling the reheat combustor 20. In an alternate embodiment of thedisclosure, both the second stream of the expanded combustion gas 32 andthe third stream of the expanded combustion gas 32 are mixed with acoolant 42 and the mixture is utilized for cooling the reheat combustor20. Coolant 42 may be introduced into the reheat combustor 20 by anysuitable means. For example, coolant 42 may be introduced through aseries of circumferentially spaced inlet nozzles placed downstream ofthe extraction location of expanded combustion gas 32, but upstream ofone or more reheat combustor liner coolant injection holes (not shown inFIG. 1), such that expanded combustion gas 32 and coolant 42 havesufficient volume and time to mix. In a specific embodiment, the coolant42 comprises compressor air. It should be noted that using somecompressor air as coolant 42 along with a portion of the expandedcombustion gas 32 for cooling still saves considerable amount ofcompressor air as compared to the conventional mechanism of cooling thereheat combustor solely by compressor air. In another embodiment, thecoolant comprises steam.

In some embodiments, the temperature of the expanded combustion gas 32is in a range of about 1500 degrees Fahrenheit to about 1600 degreesFahrenheit. In a specific embodiment, the expanded combustion gas 32 isutilized for cooling the reheat combustor 20 such that the temperatureof any metallic material of the reheat combustor 20 stays below 1700degrees Fahrenheit or lower, for example. A reheat combustor gas 44(shown in FIGS. 3 and 4) may have temperature in the range of 2200 to3200 degrees Fahrenheit depending on the engine design and operatingpoint. The amount and effectiveness of the cooling mechanisms willdictate the resulting material temperatures.

FIG. 2 shows an alternate embodiment wherein the second turbine 22 isaerodynamically coupled to the first turbine 16 but on an independentshaft 46. In this embodiment, the first turbine 16 drives the compressor12 and the second turbine 22 provides shaft power, for example to drivean electric power generator 48.

FIG. 3 illustrates a schematic view of a portion of the gas turbineengine 10 including further details. More particularly, illustrated inFIG. 3 is the gas turbine engine 10 including reheat combustor 20 andsecond turbine 22. Reheat combustor 20, as illustrated, is configuredgenerally annular in shape, about an engine centerline 76. The reheatcombustor 20 is defined by an outer liner and inner liner (describedpresently) and includes a main chamber 50, defining a combustion zone51, and a trapped vortex cavity 52. In an embodiment, the reheatcombustor 20 does not include the trapped vortex cavity 52. One or moreflame stabilization devices, referred to herein as one or more flamestabilizers 54, of which only one is shown in FIGS. 3 and 4, aredisposed therein the reheat combustor 20, and more particularly spacedabout the circumference of the annular reheat combustor 20 and extendingacross the main chamber 50 in the combustor zone 51, to provide improvedcombustion. Each of the one or more flame stabilizers 54 is disposed ina cantilevered position and extending from an outer radius of the reheatcombustor 20, in an inward direction toward the engine centerline 76.The one or more flame stabilizers 54 require an active cooling flow tosurvive for any desirable length of time. As illustrated by directionalflow arrows, an intermediate pressure turbine (IPT) oxidant exhaustflow, and more particularly the expanded combustion gas 32, is splitinto a first stream 58, a second stream 60 and a third stream 62 in thesplitting zone 18.

FIG. 4 illustrates an enlarged view of the splitting zone 18 and thereheat combustor 20 of FIG. 3. It should be noted that FIG. 4 isillustrated without the inclusion of the trapped vortex cavity 52 aspreviously described. In the splitting zone 18, the expanded combustiongas 32 is split into the first stream 58, the second stream 60 and thethird stream 62 by the design of the downstream effective flow areas ineach flow path (described presently). More particularly, the flowpathways defined by the reheat combustor 20 controls the splitting ofthe flow of the expanded combustion gas 32 into the first stream 58, thesecond stream 60 and the third stream 62 as will be described. The firststream 58 constitutes the main flow to the reheat combustor 20 andundergoes combustion in the main chamber 50, and more particularly,within the combustion zone 51, of the reheat combustor 20.

As illustrated in FIGS. 3 and 4, in an embodiment, the reheat combustor20 comprises a casing 64 and an outer liner 66. The reheat combustor 20,and more particularly due to fluid pressures created therein, isconfigured to split the expanded combustion gas 32 in such a way thatthe second stream 60 of the expanded combustion gas 32 flows through apassage 68 between the casing 64 and the outer liner 66 of the reheatcombustor 20, forming an outboard cooling circuit 70. In addition, thereheat combustor 20 is configured to split the combustion gas 32 in sucha way that the third stream 62 of the expanded combustion gas 32 flowsthrough a passage 72 between an inner liner 74 and an engine center line76, forming a portion of an inboard cooling circuit 78.

The inboard cooling circuit 78, further includes a pressure loss device80, disposed in, or positioned proximate, the passage 72, and configuredto develop a pressure differential (dP) between the second stream 60 ofexpanded combustion gas 32 and the third stream 62 of expandedcombustion gas 32. The development of this pressure differential betweenthe second stream 60 and the third stream 62 allows for a portion 82 ofthe second stream 62 to flow through the one or more flame stabiliser 54from outboard to inboard as a cooling flow, with no injection of theportion 82 of the second stream 62 into the flame, and moreparticularly, the combustion zone 51. To accomplish such, the one ormore flame stabilizer 54 is configured to provide an outlet 55, for theportion 82 of the second stream 60 of the expanded combustion gas 32passing therethrough, into the passage 72. In an embodiment, thepressure loss device 80 may be an inlet metering device 84 (FIG. 3), ablocking structure 86 (FIG. 4), or any other device capable of providingcontrol of the pressure within the passages 68 and 72 and provide forthe drawing of the portion 82 of the second stream 60 of the expandedcombustion gas 32 through the one or more flame stabilizer 54.

The flow of the portion 82 of the second stream 60 of expandedcombustion gas 32 through the one or more flame stabilizer 54 providescooling to the one or more flame stabilizer 54. This active cooling ofthe one or more flame stabilizer 54 provides for an extension in life ofthe one or more flame stabilizer 54, yet eliminates any injection of thecooling flow into a central region of the combustion zone 50. Inaddition, the portion 82 of the second stream 60 of the expandedcombustion gas 32 exiting the one or more flame stabilizer 54 at theoutlet 55 and into passage 72, provides additional cooling to the innerliner 74.

As previously indicated, the second stream 60 of expanded combustion gas32 is used to cool the outer liner 66 of the reheat combustor 20. Itshould be noted, in an embodiment, a portion of the second stream 60 ofthe expanded combustion gas 32 may be used to cool the trapped vortexcavity 52, where present. In addition, the third stream 62 of expandedcombustion gas 32 and the portion 82 of the second stream 32 of expandedcombustion gas 32 passing through the one or more flame stabilizer 54 isused to cool the inner liner 66 of the reheat combustor 20. The secondstream 60 and the third stream 62 are used to cool the reheat combustor20 through various mechanisms. In an embodiment, impingement cooling isemployed, wherein the second stream 60 and the third stream 62 areimpinged on the cold surfaces of the reheat combustor 20, that is thesurface in contact with the second stream 60 and the third stream 62,respectively. In addition, impingement cooling is employed, wherein theportion 82 of the second stream 60 is impinged on the inner surface ofthe one or more flame stabilizer 54, that is the surface in contact withthe second portion 82 of the second stream 60. In another embodiment,effusion cooling or film cooling is employed, wherein the coolingstreams, and more particularly the second stream 60 and the third stream62 are injected through one or more injection holes 88 of the inner andouter liners 66, 74 to form a thin film cooling layer over the surfaceof the reheat combustor 20 that is bounded by the reheat combustiongases 44. It is to be noted that a combination of two or more mechanismscan also be employed to cool the reheat combustor 20 using the secondstream 60 and the third stream 62.

After being utilized for cooling, the second stream 60, the portion 82of the second stream 60 passing through the one or more flame stabilizer54 that exits into the passage 72, and the third stream 62, enter themain chamber 50 of the reheat combustor 20 as illustrated in the figure.The outer liner 66 of the reheat combustor 20 may include the injectionholes 88, which facilitate the entry of the second stream 60 in the mainchamber 50. The injection holes 88 may be used for dilution or filmcooling purposes. In some embodiments, the inner liner 74 may includethe injection holes 88. After entering the main chamber 50, the secondstream 60 and the third stream 62 are mixed with the first stream 58(undergoing combustion) and in the process a fraction of the secondstream 60 and a fraction of the third stream 62 may also undergocombustion in the main chamber 50. The mixture of the combusted firststream 58, the second stream 58 (a part of which may have undergonecombustion) and the third stream 62 (a part of which may have undergonecombustion) leaves the reheat combustor 20 as the flow 33. The flow 33is expanded in the second turbine 22 (illustrated in FIG. 1).

As previously indicated, in some embodiments, the second stream 60and/or the third stream 62 may be mixed with the coolant 42 in theirrespective passage 68, 72 and the mixture is used to cool the reheatcombustor 20. In a specific embodiment, the coolant 42 is air drawn froma stage of the compressor 12 (FIG. 1). In another embodiment, thecoolant 42 is steam.

The reheat combustor 20 is configured to split the expanded combustiongas 32 based on an operating point of the gas turbine engine 10. Theoperating point can be a function of load demand, inlet air temperature,fuel type, or the like. In an embodiment, the reheat combustor 20 isconfigured such that the second stream 60 and the third stream 62,combined, are about 20% to about 45% by mass of the flow of the postcombustion gas 32.

Referring now to FIG. 5, illustrated is a method 90 for cooling a reheatcombustor 20 according to one or more embodiments. The method 90includes compressing an air stream in a compressor, as step 92. Next, apost combustion gas is generated by combusting the compressed air streamexiting from the compressor in a combustor, as step 94. In a step 96,the post combustion gases are expanded in a first turbine. Subsequent toexpansion, the expanded combustion gas exiting from the first turbine isinto a first stream, a second stream and a third stream, in step 98. Thefirst stream of the expanded combustion gas is combusted, in a step 100,in a main chamber of a reheat combustor. In a step 102, an outer linerand a flame stabilizer of the reheat combustor are cooled using thesecond stream of the expanded combustion gas. In a step 104, an innerliner of the reheat combustor is cooled using the third stream of theexpanded combustion gas and a portion of the second stream of theexpanded combustion gas passing through the one or more flamestabilizers.

In an embodiment, the method 90 further comprises, in a step 106 a,mixing the second stream of the expanded combustion gas after coolingthe outer liner and the one or more flame stabilizers of the reheatcombustor with a combusted first stream of the expanded combustion gasof the reheat combustor and mixing the third stream of the expandedcombustion gas and a portion of the second stream of the expandedcombustion gas passing through the one or more flame stabilizers aftercooling the inner liner of the reheat combustor with the combusted firststream of the expanded combustion gas of the reheat combustor. In analternative embodiment, the method 90 further comprises, in a step 106b, expanding the combusted first stream of the reheat combustor in asecond turbine and at least partially cooling the second turbine with atleast one of a portion of the second stream of the expanded combustiongas and a portion of the third stream of the expanded combustion gas.The method 90 provides for an aerodynamically efficient cooling flowpath for stable combustion.

Although only certain features of the disclosure have been illustratedand described herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the disclosure.

What is claimed is:
 1. A gas turbine engine, comprising: a compressorfor compressing air; a combustor for generating a post combustion gas bycombusting a compressed air exiting from the compressor; a first turbinefor expanding the post combustion gas; a splitting zone for splitting anexpanded combustion gas exiting from the first turbine into a firststream, a second stream, and a third stream; a reheat combustor forcombusting the first stream of the expanded combustion gas; and aradially outer liner at a radial exterior of the reheat combustor whichthe second stream is at least initially directed around; an inner linerat a radial interior of the reheat combustor which the third stream isat least initially directed around; a pressure loss device fordeveloping a pressure differential between the second stream and thethird stream; and one or more flame stabilizers traversing the reheatcombustor and containing a fluid channel with an inlet at the outerliner and an outlet at the inner liner, the one or more flamestabilizers configured to convey a portion of the second stream into theflow of the third stream.
 2. The gas turbine engine of claim 1, whereinthe splitting zone is configured to split the expanded combustion gas insuch a way that the second stream of the expanded combustion gas flowsthrough a passage between a casing and the outer liner of the reheatcombustor and the third stream of the expanded combustion gas flowsthrough a passage between an engine centerline and the inner liner ofthe reheat combustor.
 3. The gas turbine engine of claim 2, wherein thesplitting zone is configured to maintain a balance of pressures of thefirst stream, the second stream and the third stream of expandedcombustion gas to achieve sufficient flow through the reheat combustorand to provide for cooling of the reheat combustor.
 4. The gas turbineengine of claim 1, wherein the pressure loss device comprises a devicefor developing a pressure differential between the second stream and thethird stream so as to allow the portion of the second stream to be drawnthrough the one or more flame stabilizers and exit into the passagebetween the engine centerline and the inner liner of the reheatcombustor and provide for cooling of the one or more flame stabilizersand the inner liner.
 5. The gas turbine engine of claim 4, wherein thepressure loss device is one of an inlet metering device and a blockingstructure.
 6. The gas turbine engine of claim 1, further comprising atrapped vortex cavity, wherein at least the portion of the second streamof expanded combustion gases provides cooling to the trapped vortexcavity.
 7. The gas turbine engine of claim 1, wherein the at least oneof the inner liner and the outer liner of the reheat combustor comprisesinjection holes for at least a portion of one of the second stream andthe third stream of the expanded combustion gas to enter the reheatcombustor after cooling at least one of the inner liner and the outerliner of the reheat combustor and mix with a combusted first stream. 8.The gas turbine engine of claim 1, further comprising a second turbinefor expanding a mixture of a combusted first stream of expandedcombustion gas from the reheat combustor, the second stream of expandedcombustion gas and the third stream of expanded combustion gas.
 9. Thegas turbine engine of claim 1, further comprising a second turbine forexpanding a combusted first stream of expanded combustion gas from thereheat combustor and wherein at least one of a portion of the secondstream of expanded combustion gas and a portion of the third stream ofexpanded combustion gas provide at least partial cooling for the secondturbine.
 10. A method of operating a gas turbine engine, the methodcomprising: compressing an air stream in a compressor; generating a postcombustion gas by combusting a compressed air stream exiting from thecompressor in a combustor; expanding the post combustion gas in a firstturbine; splitting an expanded combustion gas exiting from the firstturbine into a first stream, a second stream and a third stream;combusting the first stream of the expanded combustion gas in a reheatcombustor, the reheat combustor including a radially outer liner at aradial exterior of the reheat combustor which the second stream is atleast initially directed around, an inner liner at a radial interior ofthe reheat combustor which the third stream is at least initiallydirected around and one or more flame stabilizers traversing the reheatcombustor and containing a fluid channel with an inlet at the outerliner and an outlet at the inner liner, the one or more flamestabilizers configured to convey a portion of the second stream into theflow of the third stream; creating a pressure differential between thesecond stream and the third stream using a pressure loss device; coolingthe outer liner and the flame stabilizer of the reheat combustor usingthe second stream of the expanded combustion gas; and cooling the innerliner of the reheat combustor using the third stream of the expandedcombustion gas and the portion of the second stream of the expandedcombustion gas passing through the one or more flame stabilizers. 11.The method of claim 10, further comprising: mixing the second stream ofthe expanded combustion gas after cooling the outer liner and the one ormore flame stabilizers of the reheat combustor with a combusted firststream of the expanded combustion gas of the reheat combustor; andmixing the third stream of the expanded combustion gas and a portion ofthe second stream of the expanded combustion gas passing through the oneor more flame stabilizers after cooling the inner liner of the reheatcombustor with the combusted first stream of the expanded combustion gasof the reheat combustor.
 12. The method of claim 10, further comprisingexpanding the combusted first stream of the reheat combustor in a secondturbine and at least partially cooling the second turbine with at leastone of a portion of the second stream of the expanded combustion gas anda portion of the third stream of the expanded combustion gas.
 13. Themethod of claim 10, wherein the second stream of the expanded combustiongas and the third stream of the expanded combustion gas, in combinationare about 20% to about 45% by mass of the expanded combustion gasexiting from the first turbine.
 14. The method of claim 10, whereincooling the outer liner and the inner liner comprises, cooling throughat least one of impingement cooling, effusion cooling, and film cooling.15. The method of claim 10, further comprising mixing the second streamof the expanded combustion gas with a coolant before cooling the outerliner and the flame stabilizer of the reheat combustor.
 16. The methodof claim 15, wherein the coolant comprises air extracted from thecompressor.
 17. The method of claim 15, wherein the coolant comprisessteam.
 18. A method comprising: splitting a flow of an expanded postcombustion gas from a first turbine into a first stream, a second streamand a third stream; combusting the first stream of the expanded postcombustion gas in a reheat combustor, the reheat combustor including aradially outer liner at a radial exterior of the reheat combustor whichthe second stream is at least initially directed around, an inner linerat a radial interior of the reheat combustor which the third stream isat least initially directed around and one or more flame stabilizerstraversing the reheat combustor and containing a fluid channel with aninlet at the outer liner and an outlet at the inner liner, the one ormore flame stabilizers configured to convey a portion of the secondstream into the flow of the third stream; creating a pressuredifferential between the second stream and the third stream using apressure loss device; cooling the outer liner and the one or more flamestabilizers of the reheat combustor using the second stream of the postcombustion gas; and cooling the inner liner of the reheat combustorusing the third stream of the post combustion gas and the portion of thesecond stream of post combustion gas passing through the one or moreflame stabilizers.
 19. The method of claim 18, wherein splitting a flowof the expanded combustion gas includes maintaining a balance ofpressures of the first stream, the second stream and the third stream toachieve sufficient flow through the reheat combustor and to provide forcooling of the reheat combustor.
 20. The method of claim 18, furthercomprising metering a pressure differential between the second streamand the third stream with a pressure loss device to allow a portion ofthe second stream to be drawn through the one or more flame stabilizersand exit into a passage between the engine centerline and the innerliner of the reheat combustor and provide for cooling of the one or moreflame stabilizers and the inner liner.